The overall objective of the proposed project is to define those factors such as the sympathetic nervous, renin-angiotensin, and prostaglandin systems on control of renal circulation and salt metabolism. It is proposed that these factors will be examined in normal animals as well as animal models of human disease, i.e. acute renal failure and hypertension. Most of these projects are presently underway. We are presently developing radioimmune assay method to measure catecholamines and prostaglandins to allow for more critical studies. We have examined some of the above factors in normal and hemorrhaged adult dogs as well as neonatal puppies. These studies have demonstrated significant differences in control of renal circulation in neonates and adult dogs. We have attempted to explain these differences. For example, neonatal kidneys have a greater sympathetic tone and are more sensitive to sympathomimetic drugs. Studies in the adult dog showed that renin release and changes in intrarenal circulation vary as independent variables probably in response to sympathetic stimulation during hemorr.